1. Field of the Invention
The present invention relates to a new and improved high energy loss fluid flow control device and more particularly to a "letdown" valve suitable for use with high temperature, highly abrasive fluids such as those developed in coal liquefaction and gasification processes.
2. Description of the Prior Art
In U.S. Pat. No. 4,044,991, assigned to the same assignee as the present invention, there is illustrated a high energy loss fluid flow control device which is designed for use as a "letdown" valve for reducing the pressure of high temperature, highly abrasive gaseous fluids such as those that are developed in coal liquefaction and gasification processes. In U.S. Pat. No. 4,044,992, also owned by the same assignee as the present invention, there is illustrated yet another high energy loss fluid flow control device designed for use in the controlled reduction of fluid pressure of high temperature, highly abrasive fluids such as coal gas developed in coal liquefaction and gasification processes.
The high energy loss fluid flow control device of the present invention comprises an improvement on the control devices shown and described in the aforementioned patents and the novel device of the present invention for greatly reduced or minimized clearance flow volumes with a novel step-taper valve design wherein fewer crevices and dead spaces are present so that solids and other materials commonly found in coal fluids do not tend to collect and thereby interfere with normal operation.
It is an object of the present invention to provide a new and improved high energy loss fluid flow control device.
More particularly, it is an object of the invention to provide a flow control device suitable for use with high temperature, highly abrasive fluids such as those developed in coal liquefaction and gasification processes.
Another object of the present invention is to provide a new and improved pressure letdown type fluid flow control device of the character described.
Yet another object of the invention is to provide a new and improved flow control device wherein the pressure drop for clearance flow is only that pressure drop occurring across one turn of the spiral flow path of the device.
Yet another object of the invention is to provide a new and improved fluid flow control device of the character described wherein any clearance flow leaking past one turn of the helical flow path joins the main control flow in the next succeeding turn.
Another object of the present invention is to provide a new and improved fluid flow control device of the character described wherein a poppet type valve member may be initially inserted into position axially of the valve body with a threading type action thereby reducing the clearance tolerance required between the interfitting members to an absolute minimum and thereby reducing clearance flow.
Still another object of the present invention is to provide a new and improved fluid flow control device of the character described wherein the valve member is moved only longitudinally with respect to the valve body in order to open and close the valve, which movement is maximized to improve control accuracy and operational stability in the pressure reduction that is accomplished.
Yet another object of the present invention is to provide a new and improved fluid flow control device wherein a spiral flow path is provided for the fluid flow having inside and outside surfaces which are parallel to a longitudinal center line or axis of the device along the length of the valve.
Still another object of the present invention is to provide a new and improved high pressure fluid flow control device wherein the forces acting on the flow control or valve are balanced to minimize the force required to move the valve member, thereby minimizing the size of actuator required.
Still another object of the present invention is to provide a new and improved fluid flow control device of the character described wherein sealing and/or packing forces on the flow control valve member are minimized.
Yet another object of the present invention is to provide a new and improved fluid flow control device of the character described wherein a large overlap is provided between the mating spiral surfaces of the valve member and valve bore thereby minimizing clearance flow losses.
Still another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described wherein improved means is provided for attaching the valve member to a control system thereby insuring against loosening of the attaching connection and providing for cushioning in order to reduce the occurence of breakage due to impact forces.
Another object of the present invention is to provide a new and improved high energy loss fluid flow control device wherein means are provided to reduce bypass leakage and compensate for differential thermal expansion of the components.
Yet another object of the present invention is to provide a new and improved high energy loss fluid flow control device wherein flow erosion on the components is minimized.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described having a spiral flow path with a substantially constant cross-sectional area.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described adapted for use with non-flashing liquids.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described having a spiral flow path with a continuously increasing cross-sectional area between a high pressure inlet and low pressure outlet.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described in the preceding object wherein the cross-sectional area of the spiral flow path is progressively increased at the same rate as the specific volume of the fluid increases due to pressure reduction.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described having a spiral flow path progressively increased in cross-sectioned area at substantially the same rate as the specific volume of the fluid increases due to pressure reduction resulting in a substantially constant velocity along the spiral flow path.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described having a spiral flow path of novel design for minimizing erosion of the flow path surfaces, eliminating fluid cavitation by controlling fluid velocity and controlling the angle of fluid flow impingement against the flow path surfaces.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described especially adapted to handle flashing liquids.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described especially adapted to handle multi-phase fluids including liquid, gas and solid constituents.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described especially adapted to handle fluids having components of widely differing specific gravities.
Another object of the present invention is to provide a new and improved high pressure fluid flow control device of the character described having a spiral flow path designed to provide a substantially constant velocity fluid flow between high pressure and low pressure ends.